Web surveys have several advantages compared to more traditional surveys with in-person interviews, telephone interviews, or mail surveys. Their most obvious potential drawback is that they may not be representative of the population of interest because the sub-population with access to Internet...

We explore the correlates of noncoverage and nonresponse in an Internet survey conducted as part of the Health and Retirement Study (HRS), a panel study of persons 50 years old and older in the US. About 30\% of HRS respondents indicated they used the Internet. Of these, 73\% expressed...

Web surveys are a popular survey mode, but the subpopulation with Internet access may not represent the population of interest. The authors investigate whether adjusting using weights or matching on a small set of variables makes the distributions of target variables representative of the...

Respondent-driven sampling is a network sampling technique typically employed for hard-to-reach populations (for example, drug users, men who have sex with men, people with HIV). Similarly to snowball sampling, initial seed respondents recruit additional respondents from their network of...

Inference from Web surveys may be affected by non-random selection of Web survey participants. One approach to reduce selection bias is to use propensity scores and a parallel phone survey. This approach uses demographic and additional so-called Webographic or lifestyle variables to balance...

Objective: Although there is a growing body of literature on sample size in multilevel or hierarchical modeling, few studies have examined the impact of group size 5. Design: We examined the impact of a group size less than five on both a continuous and dichotomous outcome in a simple two-level...

Respondent-driven sampling is a network sampling technique typi- cally employed for hard-to-reach populations (for example, drug users, men who have sex with men, people with HIV). Similarly to snowball sampling, initial seed respondents recruit additional respondents from their network of...

Respondent-driven sampling (RDS) is a sampling technique typically employed for hard-to-reach populations (for example, homeless people, people with AIDS, immigrants). Briefly, initial seed respondents recruit additional respondents from their network of friends. The recruiting process repeats...

Boosting, or boosted regression, is a recent data-mining technique that has shown considerable success in predictive accuracy. This article gives an overview of boosting and introduces a new Stata command, boost, that im- plements the boosting algorithm described in Hastie, Tibshirani, and...